Surface Chemistry Matters. How Ligands Influence Excited State Interactions between CsPbBr₃ and Methyl Viologen

Abstract

The photocatalytic properties of cesium lead bromide (CsPbBr3) perovskite nanocrystals make them attractive for designing light harvesting assemblies. Often ignored, the surface chemistry can dictate the excited state interactions of these semiconductor nanocrystals with charge-shuttling redox molecules. We have now explored the impact of CsPbBr3 nanocrystal surface modification on the excited state interactions with methyl viologen (MV2+) for three different ligand environments: prototypical oleic acid/oleylamine (OA/OAm) ligands, PbSO4-oleate capping, and didodecyldimethylammonium bromide (DDAB) ligands. Native OA/OAm ligands and PbSO4-oleate capping exhibit the strongest complexation with MV2+, whereas the bulky DDAB ligand environment shows an order of magnitude weaker complexation. The electron transfer rate constants as measured from transient absorption spectroscopy vary in the range of 1.2–3.6 × 1011 s–1 for different ligand environments. For DDAB-CsPbBr3 NCs, the efficiency of electron transfer (Φet) is 73%. Despite a protective capping layer, PbSO4-oleate capped CsPbBr3 maintains a redox-active surface which is viable for photocatalytic applications. These results highlight the impact of surface chemistry on excited state interactions of CsPbBr3 NCs and photocatalytic applications.

Highly Stable CsPbX3/PbSO4 Core/Shell Nanocrystals Synthesized by a Simple Post‐Treatment Strategy

“…For example, didodecylammonium bromide (DDAB)‐capped CsPbBr 3 NCs shows a moderate enhancement during the post‐treatment of OctAm‐SO 4 (Figure S9, Supporting Information), probably due to the branched long chains of DDAB can resist the binding between Pb 2+ and SO 4 2− , which is consistent with Kamat's work. [ 48 ]…”

“…It should be noted that the capping ligand of CsPbBr 3 NCs plays an important role in the formation of , which is consistent with Kamat's work. [48] The poor resistance of lead halide perovskite NCs against polar solvent has been a significant limitation on their future applications, which can be mainly ascribed to their ionic nature and possible detachment of capping ligands (normally OA/OAm pairs). [49,50] Herein, inert and stable PbSO 4 shell is a promising alternative to improve the unsatisfactory durability.…”

CsPbBr3–CdS heterostructure: stabilizing perovskite nanocrystals for photocatalysis

“…[6][7][8] In recent years, another quantum dot system, viz., perovskite nanocrystals (CsPbX 3 , X ¼ Cl, Br, I), has emerged as a model semiconductor QD system to probe light induced optoelectronic and photocatalytic properties. [9][10][11][12][13] We have recently elucidated the photocatalytic aspects of CsPbBr 3 QDs by probing the interfacial electron transfer to methyl viologen 14,15 and ferrocenium cation. 16 To date, the use of these perovskite quantum dots in photocatalysis has been limited only to a few nonpolar solvents.…”

Surface Functionalization of CsPbBr3 Νanocrystals for Photonic Applications

“…At room temperature, average PL lifetimes of ∼7 ns have been obtained for the OA-, DDAB-, and ZI-capped NCs and ∼12 ns for the DDAB/PbBr 2 NCs, in agreement with the literature reported range, i.e., ∼6−12 ns for OA NCs, 7−14 ns for DDAB-based NCs, and ∼7 ns for ZIcapped NCs. 15,35,38,40,58,59 The validity of the rather arbitrary assignment of the radiative lifetime to the dominant PL decay term and the associated estimation of the radiative yield in the two studied NC systems are confirmed by (i) the reasonably good resemblance of the temperature variation of the integrating PL and the radiative QY displayed in Figure 3 and (ii) the good matching of the QY values computed at room temperature with those estimated via integrating sphere PL experiments (blue data points and error), discussed earlier in the text. For the DDAB-and DDAB/PbBr 2-capped NCs, the transient PL model requires three decay components; hence, the aforementioned reasoning for the estimation of the radiative lifetime and the QY cannot be applied.…”